U.S. patent application number 10/139312 was filed with the patent office on 2003-09-18 for enhanced docsis upstream channel changes.
Invention is credited to Currivan, Bruce J., Kolze, Thomas J..
Application Number | 20030177502 10/139312 |
Document ID | / |
Family ID | 28044276 |
Filed Date | 2003-09-18 |
United States Patent
Application |
20030177502 |
Kind Code |
A1 |
Kolze, Thomas J. ; et
al. |
September 18, 2003 |
Enhanced DOCSIS upstream channel changes
Abstract
Enhanced DOCSIS upstream channel changes. A CMTS directs channel
changing of a CM, sometimes between upstream data bursts. Logical
channels, part of a single frequency channel, may be used, and the
channel changing may be performed between those logical channels.
Multiple upstream burst profiles and/or modulation densities may be
used providing high degrees of robustness, fidelity, and throughput
and allowing great channel flexibility. A CM may be switched
between channels without losing transmitter capability. Even if
some throughput rate may be sacrificed during the channel changing,
the CM will still be able to continue data throughput. Then, the
new channel may then undergo the initialization and ranging
processes thereby enabling greater throughput on that new channel.
After undergoing the initialization and ranging processes, the new
channel will then be a fully equivalent member of the CM
communication system.
Inventors: |
Kolze, Thomas J.; (Phoenix,
AZ) ; Currivan, Bruce J.; (Irvine, CA) |
Correspondence
Address: |
GARLICK HARRISON & MARKISON LLP
P.O. BOX 160727
AUSTIN
TX
78716-0727
US
|
Family ID: |
28044276 |
Appl. No.: |
10/139312 |
Filed: |
May 6, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60364063 |
Mar 13, 2002 |
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Current U.S.
Class: |
725/111 ;
725/126 |
Current CPC
Class: |
H04L 65/611 20220501;
H04N 21/6168 20130101; H04N 21/6118 20130101 |
Class at
Publication: |
725/111 ;
725/126 |
International
Class: |
H04N 007/173 |
Claims
What is claimed is:
1. An upstream channel change method, comprising: transmitting data
upstream from a cable modem to a cable modem termination system
using a first channel; using the cable modem termination system,
directing the cable modem to change the upstream data transmission
from the first channel to a second channel; changing the upstream
data transmission from the first channel to the second channel
between upstream data bursts; continuing to transmit the data
upstream from the cable modem to the cable modem termination system
using the second channel by employing a first upstream data burst
profile thereby performing continued upstream data bursting;
performing initialization and ranging processes for the second
channel; using results of the initialization and ranging processes
to identify a second upstream data burst profile; and continuing to
transmit the data upstream from the cable modem to the cable modem
termination system using the second channel by employing the second
upstream data burst profile.
2. The method of claim 1, wherein the initialization and ranging
processes comprise calculating a plurality of equalizer taps for
the second channel.
3. The method of claim 2, wherein the initialization and ranging
processes further comprise performing channel estimation of the
second channel before calculating the plurality of equalizer taps;
and wherein the calculating the plurality of equalizer taps
comprises direct calculation of the plurality of equalizer taps
using the channel estimate of the second channel.
4. The method of claim 1, wherein a frequency band is logically
partitioned into the first channel and the second channel.
5. The method of claim 1, wherein the second upstream data burst
profile comprises a higher order upstream data burst profile when
compared to the first upstream data burst profile.
6. The method of claim 1, wherein the first upstream data burst
profile comprises a QPSK modulation density; and the second
upstream data burst profile comprises a 16 QAM modulation
density.
7. The method of claim 1, wherein at least one of the first
upstream data burst profile and the second upstream data burst
profile comprises at least one of a QPSK modulation density, a 16
QAM modulation density, a 64 QAM modulation density, a 256 QAM
modulation density, and a 1024 QAM modulation density.
8. The method of claim 1, further comprising detecting a time gap
in the upstream data transmission before performing the
initialization and ranging processes for the second channel.
9. The method of claim 1, wherein the second upstream data burst
profile comprises a maximum operable modulation density for the
second channel; and the maximum operable modulation density for the
second channel being identified during the initialization and
ranging processes for the second channel.
10. The method of claim 1, wherein the second upstream data burst
profile substantially comprises the first upstream data burst
profile.
11. An upstream channel change method, comprising: transmitting
data upstream from a cable modem to a cable modem termination
system using a first channel; using the cable modem termination
system, directing the cable modem to change the upstream data
transmission from the first channel to a second channel; changing
the upstream data transmission from the first channel to the second
channel between upstream data bursts; continuing to transmit the
data upstream from the cable modem to the cable modem termination
system using the second channel by employing a QPSK modulation
density; performing initialization and ranging processes for the
second channel; using results of the initialization and ranging
processes to identify whether the second channel is operable to
support a 16 QAM modulation density; and continuing to transmit the
data upstream from the cable modem to the cable modem termination
system using the second channel by employing the 16 QAM modulation
density when the initialization and ranging processes identify that
the second channel is operable to support the 16 QAM modulation
density.
12. The method of claim 11, wherein the initialization and ranging
processes comprise calculating a plurality of equalizer taps for
the second channel.
13. The method of claim 12, wherein the initialization and ranging
processes further comprise performing channel estimation of the
second channel before calculating the plurality of equalizer taps;
and wherein the calculating the plurality of equalizer taps
comprises direct calculation of the plurality of equalizer taps
using the channel estimate of the second channel.
14. The method of claim 11, wherein a frequency band is logically
partitioned into the first channel and the second channel.
15. The method of claim 11, further comprising detecting a time gap
in the upstream data transmission before performing the
initialization and ranging processes for the second channel.
16. An upstream channel change method, comprising: initially
transmitting data upstream from a cable modem to a cable modem
termination system using a first channel by employing a 16 QAM
modulation density; using the cable modem termination system,
directing the cable modem to change the upstream data transmission
from the first channel to a second channel; changing the upstream
data transmission from the first channel to the second channel
between upstream data bursts; and continuing to transmit the data
upstream from the cable modem to the cable modem termination system
using the second channel by employing a QPSK modulation
density.
17. The method of claim 16, further comprising: detecting a time
gap in the upstream data transmission; performing initialization
and ranging processes for the second channel; using results of the
initialization and ranging processes to identify whether the second
channel is operable to support the 16 QAM modulation density; and
continuing to transmit the data upstream from the cable modem to
the cable modem termination system using the second channel by
employing the 16 QAM modulation density when the initialization and
ranging processes identify that the second channel is operable to
support the 16 QAM modulation density.
18. The method of claim 17, wherein the initialization and ranging
processes comprise calculating a plurality of equalizer taps for
the second channel.
19. The method of claim 18, wherein the initialization and ranging
processes further comprise performing channel estimation of the
second channel before calculating the plurality of equalizer taps;
and wherein the calculating the plurality of equalizer taps
comprises direct calculation of the plurality of equalizer taps
using the channel estimate of the second channel.
20. The method of claim 16, wherein a frequency band is logically
partitioned into the first channel and the second channel.
21. A cable modem communication system, comprising a cable modem; a
cable modem network segment; and a cable modem termination system
that is communicatively coupled to the cable modem via the cable
modem network segment; and wherein the cable modem transmits data
upstream to the cable modem termination system using a first
channel; the cable modem termination system directs the cable modem
to change the upstream data transmission from the first channel to
a second channel between upstream data bursts; the cable modem
continues to transmit the data upstream to the cable modem
termination system using the second channel by employing a first
upstream data burst profile thereby performing continued upstream
data bursting; the cable modem termination system performs
initialization and ranging processes for the second channel; the
cable modem termination system identifies a second upstream data
burst profile using results of the initialization and ranging
processes; and the cable modem continues to transmit the data
upstream to the cable modem termination system using the second
channel by employing the second upstream data burst profile.
22. The cable modem communication system of claim 21, wherein the
cable modem termination system calculates a plurality of equalizer
taps for the second channel during the initialization and ranging
processes.
23. The cable modem communication system of claim 22, wherein the
cable modem termination system performs channel estimation of the
second channel before calculating the plurality of equalizer taps;
and the cable modem termination system calculates the plurality of
equalizer taps using direct calculation of the plurality of
equalizer taps using the channel estimate of the second
channel.
24. The cable modem communication system of claim 21, wherein a
frequency band is logically partitioned into the first channel and
the second channel.
25. The cable modem communication system of claim 21, wherein the
second upstream data burst profile comprises a higher order
upstream data burst profile when compared to the first upstream
data burst profile.
26. The cable modem communication system of claim 21, wherein the
first upstream data burst profile comprises a QPSK modulation
density; and the second upstream data burst profile comprises a 16
QAM modulation density.
27. The cable modem communication system of claim 21, wherein at
least one of the first upstream data burst profile and the second
upstream data burst profile comprises at least one of a QPSK
modulation density, a 16 QAM modulation density, a 64 QAM
modulation density, a 256 QAM modulation density, and a 1024 QAM
modulation density.
28. The cable modem communication system of claim 21, wherein the
cable modem termination system detects a time gap in the upstream
data transmission before performing the initialization and ranging
processes for the second channel.
29. The cable modem communication system of claim 21, wherein the
second upstream data burst profile comprises a maximum operable
modulation density for the second channel; and the maximum operable
modulation density f or the second channel being identified during
t he initialization and ranging processes for the second
channel.
30. The cable modem communication system of claim 21, wherein the
second upstream data burst profile substantially comprises the
first upstream data burst profile.
31. A cable modem communication system, comprising a cable modem; a
cable modem network segment; and a cable modem termination system
that is communicatively coupled to the cable modem via the cable
modem network segment; and wherein the cable modem transmits data
upstream to the cable modem termination system using a first
channel; the cable modem termination system directs the cable modem
to change the upstream data transmission from the first channel to
a second channel between upstream data bursts; the cable modem
continues to transmit the data upstream to the cable modem
termination system using the second channel by employing a QPSK
modulation density; the cable modem termination system performs
initialization and ranging processes for the second channel; the
cable modem termination system identifies whether the second
channel is operable to support a 16 QAM modulation density; and the
cable modem continues to transmit the data upstream to the cable
modem termination system using the second channel by employing the
16 QAM modulation density when the cable modem termination system
identifies that the second channel is operable to support the 16
QAM modulation density.
32. The cable modem communication system of claim 31, wherein the
cable modem termination system calculates a plurality of equalizer
taps for the second channel during the initialization and ranging
processes.
33. The cable modem communication system of claim 32, wherein the
cable modem termination system performs channel estimation of the
second channel before calculating the plurality of equalizer taps;
and the cable modem termination system calculates the plurality of
equalizer taps using direct calculation of the plurality of
equalizer taps using the channel estimate of the second
channel.
34. The cable modem communication system of claim 31, wherein a
frequency band is logically partitioned into the first channel and
the second channel.
35. The cable modem communication system of claim 31, wherein the
cable modem termination system detects a time gap in the upstream
data transmission before performing the initialization and ranging
processes for the second channel.
36. A cable modem communication system, comprising a cable modem; a
cable modem network segment; and a cable modem termination system
that is communicatively coupled to the cable modem via the cable
modem network segment; and wherein the cable modem initially
transmits data upstream to the cable modem termination system using
a first channel by employing a 16 QAM modulation density; the cable
modem termination system directs the cable modem to change the
upstream data transmission from the first channel to a second
channel between upstream data bursts; and the cable modem continues
to transmit the data upstream to the cable modem termination system
using the second channel by employing a QPSK modulation
density.
37. The cable modem communication system of claim 36, wherein the
cable modem termination system detects a time gap in the upstream
data transmission; the cable modem termination system performs
initialization and ranging processes for the second channel; the
cable modem termination system identifies whether the second
channel is operable to support the 16 QAM modulation density using
results of the initialization and ranging processes; and the cable
modem continues to transmit the data upstream to the cable modem
termination system using the second channel by employing the 16 QAM
modulation density when the cable modem termination system
identifies that the second channel is operable to support the 16
QAM modulation density.
38. The cable modem communication system of claim 36, wherein the
cable modem termination system calculates a plurality of equalizer
taps for the second channel during the initialization and ranging
processes.
39. The cable modem communication system of claim 38, wherein the
cable modem termination system performs channel estimation of the
second channel before calculating the plurality of equalizer taps;
and the cable modem termination system calculates the plurality of
equalizer taps using direct calculation of the plurality of
equalizer taps using the channel estimate of the second
channel.
40. The cable modem communication system of claim 36, wherein a
frequency band is logically partitioned into the first channel and
the second channel.
41. An upstream channel change method, comprising: transmitting
data upstream from a cable modem to a cable modem termination
system using a first channel; using the cable modem termination
system, directing the cable modem to change the upstream data
transmission from the first channel to a second channel; changing
the upstream data transmission from the first channel to the second
channel between upstream data bursts; and continuing to transmit
the data upstream from the cable modem to the cable modem
termination system using the second channel by employing an
upstream data burst profile thereby performing continued upstream
data bursting.
42. The method of claim 41, wherein a frequency band is logically
partitioned into the first channel and the second channel.
43. The method of claim 41, further comprising: performing
initialization and ranging processes for the second channel; using
results of the initialization and ranging processes to identify at
least one additional upstream data burst profile; and continuing to
transmit the data upstream from the cable modem to the cable modem
termination system using the second channel by employing the at
least one additional upstream data burst profile; and wherein the
initialization and ranging processes comprise calculating a
plurality of equalizer taps for the second channel.
44. The method of claim 43, wherein the initialization and ranging
processes further comprise performing channel estimation of the
second channel before calculating the plurality of equalizer taps;
and wherein the calculating the plurality of equalizer taps
comprises direct calculation of the plurality of equalizer taps
using the channel estimate of the second channel.
45. The method of claim 43, wherein the at least one additional
upstream data burst profile comprises a higher order upstream data
burst profile when compared to the first upstream data burst
profile.
46. The method of claim 43, wherein the upstream data burst profile
comprises a QPSK modulation density; and the at least one
additional upstream data burst profile comprises a 16 QAM
modulation density.
47. The method of claim 43, wherein at least one of the upstream
data burst profile and the at least one additional upstream data
burst profile comprises at least one of a QPSK modulation density,
a 16 QAM modulation density, a 64 QAM modulation density, a 256 QAM
modulation density, and a 1024 QAM modulation density.
48. The method of claim 43, further comprising detecting a time gap
in the upstream data transmission before performing the
initialization and ranging processes for the second channel.
49. The method of claim 43, wherein the at least one additional
upstream data burst profile comprises a maximum operable modulation
density for the second channel; and the maximum operable modulation
density for the second channel being identified during the
initialization and ranging processes for the second channel.
50. The method of claim 43, wherein the at least one additional
upstream data burst profile substantially comprises the upstream
data burst profile.
51. An upstream channel change method, comprising: transmitting
data upstream from a cable modem to a cable modem termination
system using a first channel; using the cable modem termination
system, directing the cable modem to change the upstream data
transmission from the first channel to a second channel; changing
the upstream data transmission from the first channel to the second
channel between upstream data bursts; continuing to transmit the
data upstream from the cable modem to the cable modem termination
system using the second channel by employing a first upstream data
burst profile thereby performing continued upstream data bursting;
calculating a plurality of equalizer taps for the second channel
using at least one of a preamble and data of one of the upstream
data bursts; using results of the equalizer tap calculation to
identify a second upstream data burst profile; and continuing to
transmit the data upstream from the cable modem to the cable modem
termination system using the second channel by employing the second
upstream data burst profile.
52. The method of claim 51, further comprising calculating at least
one additional plurality of equalizer taps for the second channel
using the data of one of the upstream data bursts, the at least one
additional plurality of equalizer taps for the second channel
comprising an improved estimate of the plurality of equalizer taps
for the second channel; using results of the at least one
additional equalizer tap calculation to identify a third upstream
data burst profile; and continuing to transmit the data upstream
from the cable modem to the cable modem termination system using
the second channel by employing the third upstream data burst
profile.
53. The method of claim 52, wherein the first modulation density
comprises a QPSK modulation density; the second modulation density
comprises a 16 QAM modulation density; and the third modulation
density comprises a 64 QAM modulation density.
54. The method of claim 52, wherein the first modulation density
comprises a QPSK modulation density; the second modulation density
comprises a 64 QAM modulation density; and the third modulation
density comprises a 16 QAM modulation density.
55. The method of claim 51, further comprising performing channel
estimation of the second channel before calculating the plurality
of equalizer taps.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present U.S. Utility Patent Application claims priority
pursuant to 35 U.S.C. .sctn. 119(e) to U.S. Provisional Patent
Application Serial No. 60/364,063, entitled "ENHANCED DOCSIS
UPSTREAM CHANNEL CHANGES," (Attorney Docket No. BP 2098), filed
Mar. 13, 2002, pending, which is hereby incorporated herein by
reference in its entirety and is made part of the present Utility
Patent Application for all purposes.
TECHNICAL FIELD OF THE INVENTION
[0002] The invention relates generally to communication systems;
and, more particularly, it relates to cable modem communication
systems.
BACKGROUND OF THE INVENTION
[0003] Data communication systems have been under continual
development for many years. Cable modem (CM) communication systems
have been of particular interest in the past several years, given
their operable bandwidth and data rates being significantly greater
than many other forms of communication systems. This is particular
in the case of Internet access for individual subscribers. A CM
communication system typically involves communication between a CM
and a cable modem termination system (CMTS). The upstream within
the CM communication system often involves the changing of upstream
communication (from CM to CMTS) from one channel to another. In a
typical CM communication system employing the Data Over Cable
Service Interface Specification (DOCSIS), the original channel has
undergone already initialization and ranging processes to provide
for optimal upstream communication performance on that particular
channel.
[0004] Cable-based communications systems are used to carry many
types of information, including video programming, voice services,
data services, etc. Data services may themselves include video,
audio, voice, and other real-time services as well as best-effort
Internet Protocol (IP) services such as email, web surfing, and
file transfer. DOCSIS is a commonly used standard for data
communication in cable systems. DOCSIS is intended to guarantee
interoperability among equipment from different vendors. It
specifies the behavior of the cable data communication system and
its parts on a number of levels. It includes system and plant
architecture requirements; physical-layer specifications covering
the transmission of physical signals on the cable plant, including
frequency plan, modulation, coding, fidelity requirements, etc.;
Medium Access Control (MAC) layer specifications covering the
format, timing, and management of data transmissions, including
packet formats, management messaging, error handling, et al.; and
specifications for interfaces in areas such as connection of a
users' computer, connection of headend equipment to other networks
(e.g. a WAN or the Internet), network management functionality, et
al.
[0005] In a DOCSIS system, a single Cable Modem Termination System
(CMTS) acts as a supervisory node. One or more Cable Modems (CMs)
act as client nodes. The CMTS generally resides at a cable headend
or other operator site, while the CMs reside at the customer
premises. The CMTS transmits downstream data traffic in a broadcast
manner, i.e. so that it is received by all CMs. Besides data
associated with services being provided, this downstream data also
includes various kinds of management messages that provide the CMs
with MAC information such as when the CM is allowed to transmit,
what physical layer parameters it must use, etc. The CM will use
this information to transmit upstream data to the CMTS in a
point-to-point fashion, i.e. only the CMTS can "hear" the
transmissions of the CM. The CMTS manages the CMs in such a way as
to guarantee that no CM's transmissions will interfere with those
of another CM so that each CM's transmissions may be properly
received (except in designated regions, known as "contention"
regions, in which multiple CMs are allowed to transmit and may
collide with each other). To guarantee this, DOCSIS provides for
separation of CM transmissions in time, in frequency, or in
codes.
[0006] As one tool for separating CM transmission, DOCSIS includes
a construct called a channel. A channel is defined by an Upstream
Channel Descriptor (UCD) message, a type of MAC-layer management
message which is sent downstream by the CMTS to all CMs. A UCD
includes a Channel ID (which is an arbitrary 8-bit identifier for
the channel) and a number of parameters which define the
physical-layer associated with a channel (e.g. center frequency,
methods of coding, preamble length, etc.). In a given system, the
CMTS may have any number of channels active; for each channel, it
periodically sends a UCD message describing that channel. A
particular CM will either choose a specific channel to operate on
or be instructed by the CMTS to operate on a specific channel.
Typically, a channel will have a large number (tens to hundreds) of
CMs operating on it at the same time. All CMs on a single channel
must use the same physical layer parameters, as specified by the
UCD message.
[0007] In versions of DOCSIS prior to 2.0, the frequency plan of
the various active channels is organized such that channels
operating on the same physical segment of the cable plant used
different center frequencies chosen such that there is little or no
spectral overlap between channels, thus providing separation in
frequency of groups of CMs. Within each channel, the CMTS then
schedules the upstream transmissions of the various CMs in a Time
Division Multiple Access (TDMA) fashion so that each CM received
the desired number and frequency of transmit opportunities with no
overlap between CMs (except for contention regions open to multiple
CMs). The CMTS transmits a MAC layer management message known as an
Upstream Bandwidth Allocation message, or MAP message, to indicate
to the CMs the allocation of time slots on a particular
channel.
[0008] A MAP message defines the use to which each time slot may be
put on a particular channel. Separate MAP messages are sent for
each channel. The MAP messages for a channel contain a Channel ID
field matching that of the UCD messages for that same channel. A
MAP message generally also includes information about time slots on
the channel. This information includes: the slot's start time; its
duration; the CM or CMs which are allowed to use that slot; and the
type of transmission it or they may use the slot for. Transmission
type is specified by an Interval Usage Code (IUC). Each IUC has a
designated purpose, e.g. for requests, for long data transmissions,
for short data transmissions, for maintenance activities, et al.
When the MAP indicates that a particular CM may use a given time
slot, the CM may transmit a burst of the specified type during that
time slot. A burst is defined by the period during which the CMs
transmitter is on. The CMs transmitter must be off during any
timeslot in which the CMTS has not specifically given that CM (or a
group of CMs to which it belongs) permission to transmit.
[0009] DOCSIS 2.0 adds new tools for separating the transmissions
of the various CMs. One such tool is Synchronous Code Division
Multiple Access (S-CDMA). With S-CDMA, transmissions from various
CMs are still scheduled in time; however, at a given time, more
than one CM may be physically transmitting using a particular set
of codes. The codes chosen are orthogonal so that each CMs
transmission may be independently recovered at the receiver,
providing for separation and management of CM transmissions via
codes.
[0010] DOCSIS 2.0 also introduces the concept of a "logical
channel." In contrast with DOCSIS 1.1, where each channel on a
single physical plant segment must use a different center
frequency, DOCSIS 2.0 allows the coexistence of multiple "logical
channels" using the same spectrum on the same physical plant
segment. Each logical channel is described by its own UCD message;
this allows CMs on different logical channels to use different
physical layer parameters (although all CMs on the same logical
channel must use the same physical layer parameters). To prevent
these logical channels from interfering with each other, the CMTS
schedules the various logical channel using a particular spectrum
for different time slots, so that at any given time only one such
logical channel is transmitting, while the others are scheduled for
idle slots during this time. Thus, the CMTS manages these logical
channels in such a way as to separate them in time. The term
"physical channel" is sometimes used to refer to the particular
part of the available spectrum which is being shared among logical
channels, while the term "logical channel" is used to refer to one
of the channels as described by a UCD message which occupies the
spectrum of the physical channel. The coexistence of multiple
logical channels within a physical "channel" is completely
transparent to the CM; thus, the concept of a "logical channel" is
only meaningful at the CMTS, where the sharing of spectrum is
visible. The CM behaves as instructed by the CMTS via the UCD and
MAP messages for the channel, which contain no information about
spectral sharing, and therefore the term "channel" (not "logical
channel") is applicable at the CM.
[0011] A UCD message defines a channel. In order to operate on a
channel, a CM must receive a UCD message describing that channel. A
UCD message contains two types of physical layer parameters:
channel-wide parameters, which are used for all transmissions on
the channel, regardless of burst type; and burst-specific
parameters, which may be different for different types of bursts
(i.e. for different IUCs). Examples of channel-wide parameters are
center frequency, coding type (S-CDMA or TDMA), preamble pattern,
et al. Examples of burst-specific parameters are modulation order
(e.g. QPSK, 16QAM, 64QAM, et al.), forward error correction (FEC)
codeword size, number of FEC parity bytes, byte interleaver matrix
size, et al. Burst-specific parameters are typically chosen so as
to maximize the efficiency of each burst type; for example, a short
data grant burst type may be specified to use a relatively short
FEC codeword size to provide a reasonable level of error correction
ability, but such codeword sizes would be very inefficient for a
long data grant burst type and thus this type may use a relatively
long FEC codeword size instead. The set of burst-specific
parameters for all allowed burst types is known as the set of
"burst profiles" for that channel. Burst profiles are properties of
a channel; thus, all modems on a channel must use the same set of
burst profiles. Thus, although long data bursts may use different
parameters than short data bursts, a modem on a given channel must
use the same parameters for transmitting short data bursts as all
other modems on a given channel. Burst profiles may be chosen to
balance any of a number of considerations, such as efficiency,
robustness in the presence of certain types of noise, etc.
[0012] DOCSIS specifies that UCD messages containing the
descriptions of the upstream channels in the system be sent
periodically by the CMTS. In general, the periodic UCD messages
describing a particular channel are always the same (they must be
sent periodically to provide information about the channel to new
CMs attempting to join the network). Thus, once established, the
parameters of a particular channel (as described by a UCD message
with a particular Channel ID) do not change. If the CMTS wishes to
change the parameters of a channel (perform a "UCD change"), it
must follow strict rules regarding notification of CMs of the
upcoming change, timing of the change, and coordination of the
change with MAP messages on the channel. A UCD change affects all
CMs currently on the channel; i.e., all CMs on the channel must
begin using the new parameters at the specified time.
[0013] When a CM first joins the network, it chooses a particular
upstream channel on which to operate (or is instructed by the CMTS
to operate on a particular upstream channel) and performs an
intialization process. This initialization process includes a step
known as ranging, whereby the CM and CMTS cooperate to determine
what timing offsets the CM must apply to its transmission (based on
the distance between CM and CMTS), what transmit pre-equalizer
coefficients (if any) the CM must use when transmitting (based on
the physical characteristics of the channel in use), and possibly
other parameters individual to this CM. Once this ranging process
is complete, the CM can transmit upstream data in a manner which
will not interfere with other CMs and will be properly received at
the CMTS. The initialization process may include other steps as
well (e.g. authentication, registration on the network, etc.). When
initialization is complete, the CMTS will allow the CM to pass data
traffic on the channel. This data traffic may include best-effort
services such as email or web traffic, and it may also include real
time services such as voice (e.g., using VoIP [Voice over Internet
Protocol]), video, audio, two-way video- or audio-conferencing,
etc.
[0014] Sometimes it is desirable for the CMTS to instruct a
particular CM to move from one channel to another. This may be done
for a number of purposes. The operator may wish to perform "load
balancing" by moving CMs from a heavily loaded channel onto a
lightly loaded one. Or the operator may wish to perform system
maintenance, perhaps involving the swapping or upgrading of headend
equipment, which requires that a particular card, shelf, cabling
segment, etc. be free of traffic. At the time the operator wishes
to move a CM from one channel to another, the CM may or may not be
actively passing traffic. In general, it is not possible to make
channel changes only on CMs which are not actively passing traffic.
This is particularly true in a system which provides real-time
services, when a session (e.g. a phone call) may be in progress at
the time the channel change is desired.
[0015] DOCSIS provides a mechanism called Dynamic Channel Change
(DCC) for the purpose of moving a single CM from one channel to
another. The messaging involved in this process is complex and
affects many layers of the system. The process may be briefly
summarized by the following steps: (1) CMTS instructs CM to change
channels, and optionally provides the UCD parameters of the "new"
channel and/or specifies which portions of the normal
initialization process must be performed by the CM after it
switches channels and before beginning to pass traffic on the new
channel; (2) CM acknowledges receiving the channel change
instruction; (3) CM stops transmitting on the old channel; (5) CM
switches to the new channel and performs whatever initialization
steps were specified by the CMTS; (6) CM begins transmitting on the
new channel.
[0016] A problem with the current state of the art lies in the
initialization steps. These steps must be performed in order for
the CM to transmit successfully on the new channel without
interfering with other CMs' transmissions, and may take several
seconds or more to complete. During this initialization period, the
CM is unable to transmit normal data traffic. If the CM is carrying
real-time services, the gap in transmission due to initialization
on the new channel may result in complete loss of the real-time
connection (e.g. dropping of the phone call). This behavior is
unacceptable in a modem communications system. Even if the gap is
short enough that the connection is not dropped, it may result in
lost packets and/or jitter on the periodicity of the packets,
either or both of which could cause unacceptable degradation of the
quality of the connection.
[0017] DOCSIS allows for the possibility of reducing the delay due
to re-initialization on a new channel by allowing the CMTS to
specify which initialization steps, if any, must be taken by the CM
when it moves to the new channel. However, in many cases it may not
be physically possible to omit certain initialization steps. For
example, if a CM is instructed to move to a new channel with a
substantially different center frequency, the transmit
pre-equalizer coefficients needed by the CM to operate on this new
channel may be very different from those which were used on the old
channel, and thus a process of ranging is required to determine
these coefficients before the CM can successfully transmit on the
new channel. Similary, the new channel may use burst profiles which
are chosen for maximum efficiency (e.g. high order modulation,
little FEC) but require great precision in transmit timing and/or
equalization; this precision may not be physically achievable
without a process of ranging and its inherent delay. Because of the
physically necessity of re-initialization, there may be very few to
zero combinations of channels between which a CM may perform a DCC
while carrying real-time traffic without unacceptably degrading or
dropping the real-time connection. This places a serious limitation
on operators who wish to support such services.
[0018] The present invention seeks to address the deficiencies of
the prior art by providing methods for performing channel changes
while maintaining acceptable quality of real-time services
(ideally, zero jitter and zero packet loss). The present invention
does this by providing an intermediate channel (or channels) as a
"stepping stone" between the channel the CM is currently operating
on and the channel on which it is ultimately desired that the CM
operate. This allows the CM to perform the channel change in
relatively small steps, each of which may be taken without the need
for an immediate re-initialization process. Once the CM has been
moved to such an intermediate channel, the CMTS may provide it with
a maintenance opportunity at a convenient time, during which
adjustments may be made to the CM's timing offset, transmit
pre-equalizer coefficients, et al. These adjustments bring the CM's
operating parameters closer to those needed for successful
operation on the ultimate destination channel. After the
adjustments are made, the CM is then able to take the next step,
again without the need for an immediate ranging or other
initialization process.
[0019] The present invention is described in the context of a
DOCSIS system. However, the concept may apply to other systems
using other protocols.
[0020] Further limitations and disadvantages of conventional and
traditional systems will become apparent to one of skill in the art
through comparison of such systems with the invention as set forth
in the remainder of the present application with reference to the
drawings.
SUMMARY OF THE INVENTION
[0021] Various aspects of the invention can be found in a CM
communication system that is operable to perform upstream channel
changes that are sometimes performed, without disrupting upstream
data transmissions. The present invention is operable to enable
channel changing for upstream data bursts (from a CM to a CMTS)
within a CM communication system. The present invention provides
for ensuring operation on the new channel in a very robust manner,
thereby guaranteeing proper operation during the upstream data
bursting. The present invention then enables continued transmission
following the channel changing. This may involve changing from one
channel to another channel with a substantially similar center
frequency. In some embodiments, a number of logical channels are
used in a single frequency channel, or frequency band, the channel
changing may be performed between those logical channels. A variety
of upstream burst profiles and/or modulation densities may be
employed thereby providing a high degree of robustness, fidelity,
and throughput while that allows multiple programmable
flexibilities on each channel. If desired, the number of available
upstream burst profiles and/or modulation densities may be
selectable and programmable by a designer of the CM communication
system.
[0022] A CM may be switched from one channel to another, more
efficiently, minimizing interruption, and thus maintaining data
flows and not disrupting data transmission. Some throughput rate
may be sacrificed, by switching to a lower order upstream burst
profile and/or lower order modulation density, yet the CM will be
able to continue data throughput. Then, after meeting some
condition, the new channel, to which the CM has been switched, may
then undergo the initialization and ranging processes thereby
enabling greater throughput on that new channel. After undergoing
the initialization and ranging processes, the new channel will then
be a fully equivalent member of the CM communication system.
[0023] The above-referenced description of the summary of the
invention captures some, but not all, of the various aspects of the
present invention. The claims are directed to some other of the
various other embodiments of the subject matter towards which the
present invention is directed. In addition, other aspects,
advantages and novel features of the invention will become apparent
from the following detailed description of the invention when
considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] A better understanding of the invention can be obtained when
the following detailed description of various exemplary embodiments
is considered in conjunction with the following drawings.
[0025] FIG. 1 is a system diagram illustrating an embodiment of a
CM communication system that is built according to the present
invention.
[0026] FIG. 2 is a system diagram illustrating another embodiment
of a CM communication system that is built according to the present
invention.
[0027] FIG. 3 is a system diagram illustrating another embodiment
of a CM communication system that is built according to the present
invention.
[0028] FIG. 4 is a system diagram illustrating another embodiment
of a CM communication system that is built according to the present
invention.
[0029] FIG. 5 is a system diagram illustrating an embodiment of a
CMTS system that is built according to the present invention.
[0030] FIG. 6 is a functional block diagram illustrating an
embodiment of CMTS functionality that is performed according to the
present invention.
[0031] FIG. 7 is a functional block diagram illustrating another
embodiment of CMTS functionality that is performed according to the
present invention.
[0032] FIG. 8 is a diagram illustrating an embodiment of an
upstream communication logical channel partition according to the
present invention.
[0033] FIG. 9A is a diagram illustrating an embodiment of example
upstream burst profiles according to the present invention.
[0034] FIG. 9B is a diagram illustrating an embodiment of example
modulation densities according to the present invention.
[0035] FIG. 10 is a flowchart illustrating an embodiment of a CM
upstream channel change method that is performed according to the
present invention.
[0036] FIG. 11 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0037] FIG. 12 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0038] FIG. 13 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0039] FIG. 14 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0040] FIG. 15 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0041] FIG. 16 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0042] FIG. 17 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
[0043] FIG. 18 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0044] The present invention is operable to enable channel changing
without disrupting upstream data transmissions (from a CM to a
CMTS) within a CM communication system. A CM may be switched from
one channel to another, more efficiently, minimizing interruption,
and thus maintaining data flows and not disrupting data
transmission. The present invention provides for ensuring operation
on the new channel in a very robust manner, thereby guaranteeing
proper operation for the upstream data burst. The present invention
then enables continued transmission during the channel changing.
This may involve changing from one channel to another channel with
a substantially similar center frequency. In some embodiments, a
number of logical channels are used in a single frequency channel,
or frequency band, the channel changing may be performed between
those logical channels. A variety of upstream burst profiles and/or
modulation densities may be employed thereby providing a high
degree of robustness, fidelity, and throughput while that allows
multiple programmable flexibilities on each channel. If desired,
the number of available upstream burst profiles and/or modulation
densities may be selectable and programmable by a designer of the
CM communication system.
[0045] A CM may be switched from one channel to another without
forcing the CM to lose its transmitter capability. Some throughput
rate may be sacrificed, by switching to a lower order upstream
burst profile and/or lower order modulation density, yet the CM
will be able to continue data throughput. Then, after meeting some
condition, the new channel to which the CM has been switched, may
then undergo the initialization and ranging processes thereby
enabling greater throughput on that new channel. The optimal
transmitter equalizer taps may be calculated when performing the
ranging process. After undergoing the initialization and ranging
processes, the new channel will then be a fully equivalent member
of the CM communication system.
[0046] The operation of the present invention may also be described
as follows: sometimes, the CMTS orders a CM to switch channels
between upstream data bursts. While within prior art systems, this
may not even be possible (given the requirements of undergoing the
initialization and ranging processes), this may result in
significantly reduced performance. The data in the next upstream
data burst may be lost altogether, while the new channel must
undergo similar initialization and ranging processes before
beginning an upstream data burst on that new channel.
[0047] In the prior art approach, there would be no knowledge of
the integrity of a new channel to which the CM is to change. There
would be no knowledge of how corrupted that new channel may in fact
be. Some designs of upcoming versions of DOCSIS have arrived at the
conclusion that channel changing between upstream data bursts is
too onerous on the communication system's resources and/or is
simply not feasible. However, the present invention enables channel
changing between upstream data bursts. In addition, channel
changing may be performed between upstream data bursts without
having to undergo the initialization and ranging processes
immediately. The upstream data burst may begin and the data
throughput may be continued without undergoing these initialization
and ranging processes, and they may be performed later on when
there are available processing resources within the CM
communication system.
[0048] In certain embodiments, a second channel (or multiple
channels) that may be viewed as being a "dual" channel at (nearly)
the same center frequency as a primary channel may be maintained in
order to increase the number of burst profiles available over that
frequency range. This supports a Dynamic Channel Change (DCC), and
may be performed at the CMTS within the CM communication system.
The present invention provides a solution that is backwards
compatible with DOCSIS 1.0 and 1.1 compatible CMs.
[0049] In one embodiment, the upstream data burst on the new
channel is initially performed using a relatively low order
upstream burst profile and/or lower order modulation density
thereby enabling the CM to continue data throughput to the CMTS.
For example, the low order upstream burst profile and/or lower
order modulation density may involve employing Quadrature Phase
Shift Keying (QPSK) thereby providing a high degree of robustness.
There can be relatively high confidence that the new channel will
be able to support QPSK. Afterwards, when possible, the new channel
may undergo initialization and ranging and a higher order upstream
burst profile and/or higher order modulation density may be
employed to provide a higher degree of throughput. For example, the
higher order upstream burst profile and/or lower order modulation
density may involve employing QAM (Quadrature Amplitude Modulation)
of various higher orders, such as 16 QAM, 64 QAM, 256 QAM, and 1024
QAM.
[0050] Some proposed DOCSIS solutions employ only QPSK and 16 QAM;
in such CM communication systems, the use of the lower order and
higher order modulation densities may involve switching between
QPSK and 16 QAM. For example, the present invention may start out
with QPSK on the new channel for an individual CM. This may permit
operation without using ideal equalizer taps on that new channel.
While this may result in lower throughput for that CM, a call at
least won't be dropped. After some period (as determined when some
predetermined conditions are met), station maintenance may be
performed that may involve performing initialization and ranging
processes, calculating better equalizer taps, and/or changing to
higher order modulation densities. This will perform well for Time
Division Multiple Access (TDMA) and also presents a much simpler
solution when compared to prior art approaches. In addition, a
lower order upstream data burst profile, that involves a QPSK
modulation density, may be initially employed on the new channel.
All short grants on the new channel may be constrained to be
upstream data burst profile that employs the QPSK modulation
density.
[0051] The following example may illustrate the operation of the
present invention on one embodiment. There is a CHA (channel A)
that operates at center frequency of substantially 20 MHz, with its
burst profiles. These burst profiles are perhaps high density
constellations with limited Forward Error Correction (FEC, a
receiver technique for correcting errors in the received data) for
the most part. This would perhaps include a relatively clean
communication channel. In addition, there is another CHB (channel
B) that has also has a center frequency of substantially 20 MHz.
However, the CHB has an entirely new set of burst profiles at its
disposal. The burst profiles for the CHB may be relatively low
density constellations, with long preambles, lots of guard time,
lots of FEC, and other encoding employed within relatively lower
order burst profiles.
[0052] A CM that changes channels to 20 MHz would first go to CHB.
Then, the CM would get some synchronization and equalizer (EQ)
updates while operating here, and eventually the CM would be able
to "move" to CHA. This may be viewed as enabling the more efficient
burst profiles. From certain perspectives, a medium access
controller (MAC) is able to support this functionality. There are
some scheduler considerations here as well. It is also noted that
the channels A and B cannot hand out grants for the same time
slots.
[0053] The availability of a second channel, to increase the number
of burst profiles, for example to provide ultra-robust profiles,
does not mean that any CMs need necessarily ever use this channel.
The CMTS does not have to waste capacity (in the form of upstream
time slots) just because of the existence of this second set of
burst profiles corresponding to the second channel. All channels
could be viewed as having these dual-universe, ultra-robust
profiles/second channels available for use. When it is time to
change a modem (execute a DCC) then one of these pre-existing,
robust, alternate universe channels would be the transition
channel. There may be several CMs that are moving, so it could be
more than one CM being placed into a transitory channel, but maybe
not a lot of CMs.
[0054] Since this is just a transitory channel, it need not be in
use for a period of time under this approach. The throughput
capacity losses would be only for a limited period of time; this
would not be unlike a throughput loss from just having a modem drop
back to a lesser efficient burst profile. Moreover, using less
efficient burst profiles for a CM impacts the entire networks'
overall efficiency, for that matter.
[0055] FIG. 1 is a system diagram illustrating an embodiment of a
CM communication system 100 that is built according to the present
invention. The CM communication system includes a number of CMs
(shown as a CM user #1 111, a CM user #2 115, . . . , and a CM user
#n 121) and a CMTS 120. The CMTS 130 is a component that exchanges
digital signals with CMs on a cable network.
[0056] Each of a number of CM users, shown as the CM user #1 111,
the CM user #2 115, . . . , and the CM user #n 121, is able to
communicatively couple to a CM network segment 199. A number of
elements may be included within the CM network segment 199, as
understood by those persons having skill in the art. For example,
routers, splitters, couplers, relays, and amplifiers may be
contained within the CM network segment 199 without departing from
the scope and spirit of the invention.
[0057] The CM network segment 199 allows communicative coupling
between a CM user and a cable headend transmitter 120 and/or a CMTS
130. In some embodiments, the cable headend transmitter 120 is in
fact contained within the CMTS 130. In other embodiments, the cable
headend transmitter 120 is located externally to the CMTS 130. The
CMTS 130 may be located at a local office of a cable television
company or at another location within a CM communication system.
For example, the CMTS 130 may be located externally to a cable
headend transmitter 120. In alternative embodiments, a CMTS 135 may
be located within the cable headend transmitter 120. In the
following description, the CMTS 130 is used for illustration; yet,
those persons having skill in the art will appreciate that the same
functionality and capability as described for the CMTS 130 may
equally apply to embodiments that alternatively employ the CMTS
135. The cable headend transmitter 120 is able to provide a number
of services including those of audio, video, local access channels,
as well as any other service known in the art of cable systems.
Each of these services may be provided to the one or more CM users
111, 115, . . . , and 121.
[0058] In addition, through the CMTS 130, the CM users 111, 115, .
. . , 121 are able to transmit and receive data from the Internet,
. . . , and/or any other network to which the CMTS 130 is
communicatively coupled. The operation of a CMTS, at the
cable-provider's head-end, may be viewed as providing many of the
same functions provided by a digital subscriber line access
multiplexor (DSLAM) within a digital subscriber line (DSL) system.
The CMTS 130 takes the traffic coming in from a group of customers
on a single channel and routes it to an Internet Service Provider
(ISP) for connection to the Internet, as shown via the Internet
access. At the head-end, the cable providers will have, or lease
space for a third-party ISP to have, servers for accounting and
logging, dynamic host configuration protocol (DHCP) for assigning
and administering the Internet protocol (IP) addresses of all the
cable system's users, and typically control servers for a protocol
called Data Over Cable Service Interface Specifications (DOCSIS),
the major standard used by U.S. cable systems in providing Internet
access to users.
[0059] The downstream information flows to all of the connected CM
users 111, 115, . . . , 121; this may be viewed to be in a manner
that is similar to that manner within an Ethernet network. The
individual network connection, within the CM network segment 199,
decides whether a particular block of data is intended for it or
not. On the upstream side, information is sent from the CM users
111, 115, . . . , 121 to the CMTS 130; on this upstream
transmission, the users within the CM users 111, 115, . . . , 121
to whom the data is not intended do not see that data at all. As an
example of the capabilities provided by a CMTS, the CMTS will
enable as many as 1,000 users to connect to the Internet through a
single 6 MHz channel. Since a single channel is capable of 30-40
megabits per second of total throughput, this means that users may
see far better performance than is available with standard dial-up
modems. Embodiments implementing the present invention are
described below and in the various Figures that show the data
handling and control within one or both of a CM and a CMTS within a
CM system that operates by employing SCDMA.
[0060] The CMs of the CM users 111, 115, . . . , 121 and the CMTS
130 communicate synchronization information to one another to
ensure proper alignment of transmission from the CM users 111, 115,
. . . , 121 to the CMTS 130. This is where the synchronization of
the SCDMA communication systems is extremely important. When a
number of the CMs all transmit their signals at a same time such
that these signals are received at the CMTS 130 on the same
frequency and at the same time, they must all be able to be
properly de-spread and decoded for proper signal processing.
[0061] Each of the CMs users 111, 115, . . . , 121 is located a
respective transmit distance from the CMTS 130. In order to achieve
optimum spreading diversity and orthogonality for the CMs users
111, 115, . . . , 121 to transmission of the CMTS 130, each of the
CM transmissions must be synchronized so that it arrives, from the
perspective of the CMTS 130, synchronous with other CM
transmissions. In order to achieve this goal, for a particular
transmission cycle, each of the CMs 111, 115, . . . , 121 will
typically transmit to the CMTS 130 at a respective transmission
time, which will likely differ from the transmission times of other
CMs. These differing transmission times will be based upon the
relative transmission distance between the CM and the CMTS 130.
These operations may be supported by the determination of the round
trip delays (RTPs) between the CMTS 130 and each supported CM. With
these RTPs determined, the CMs may then determine at what point to
transmit their SCDMA data so that all CM transmissions will arrive
synchronously at the CMTS 130.
[0062] The present invention enables channel changing for each of
the CM users (CMs users 111, 115, . . . , 121) when performing
upstream data bursts to the CMTS 130. All of the functionality
described herein this patent application may be performed within
the context of the CM communication system of the FIG. 1. The FIG.
1 shows just one embodiment where the various aspects of the
present invention may be implemented. Several other embodiments are
described as well.
[0063] FIG. 2 is a system diagram illustrating another embodiment
of a CM communication system 200 that is built according to the
present invention. From certain perspectives, the FIG. 2 may be
viewed as a communication system allowing bidirectional
communication between a customer premise equipment (CPE) 240 and a
network. In some embodiments, the CPE 240 is a personal computer or
some other device allowing a user to access an external network.
The network may be a wide area network (WAN) 280, or alternatively,
the Internet 290 itself. For example, the CM communication system
200 is operable to allow Internet protocol (IP) traffic to achieve
transparent bidirectional transfer between a CMTS-network side
interface (CMTS-NIS: viewed as being between the CMTS 230 and the
Internet 290) and a CM to CPE interface (CMCI: viewed as being
between the CM 210 and the CPE 240).
[0064] The WAN 280, and/or the Internet 290, is/are communicatively
coupled to the CMTS 230 via a CMTS-NIS. The CMTS 230 is operable to
support the external network termination, for one or both of the
WAN 280 and the Internet 290. The CMTS 230 includes a modulator and
a demodulator to support transmitter and receiver functionality to
and from a CM network segment 299. A number of elements may be
included within the CM network segment 299, as understood by those
persons having skill in the art. For example, routers, splitters,
couplers, relays, and amplifiers may be contained within the CM
network segment 299 without departing from the scope and spirit of
the invention. The CM network segment 299 allows communicative
coupling between a CM user and the CMTS 230.
[0065] The CMTS 230 is operable to direct upstream channel changing
for upstream data bursts from the CM 210 to the CMTS 230. This may
be viewed as directing the particular channels by which the CM 210
is able to send upstream data bursts to the CMTS 230. The
particular channels may themselves be logical channels of a single
frequency band, or alternatively they may be physical distinct
channels separated in frequency. The upstream data burst
functionality provided by the interaction of the CMTS 230 with the
CM network segment 299 allows for more robust operation of the CM
communication system 200 when compared to prior art approaches.
[0066] FIG. 3 is a system diagram illustrating another embodiment
of a CM communication system 300 that is built according to the
present invention. The CM communication system 300 includes a CM
310 that is operable to perform upstream communication 399 to a
CMTS 330. The bandwidth of the upstream communication 399, from the
CM 310 to the CMTS 330, is partitioned into a number of channels in
the FIG. 3. This partitioning may involve logical partitioning of
the channels of a single frequency band, or alternatively the
partitioning may involve physical portioning of the available
bandwidth into distinct channels that are separated in
frequency.
[0067] The CMTS 330 is operable to direct upstream channel changing
for upstream data bursts from the CM 310 to the CMTS 330. As shown
in the upstream communication 399, the number of channels (shown as
a CH1, CH2, CH3, . . . , and CHn) are the available channels over
which the CMTS 330 may change the upstream data bursting of the CM
310 to the CMTS 330. The channel changing may be performed between
upstream data bursts while maintaining a high degree of robustness
and continued operation. In addition, the channel changing may be
performed between upstream data bursts without requiring
initialization and ranging processes to be performed before
changing to another channel. The present invention offers a
solution that allows the channel changing to a new channel without
requiring any prior knowledge of the state of corruption or the
capabilities of the network channel thereby offering continued
operation.
[0068] FIG. 4 is a system diagram illustrating another embodiment
of a CM communication system 400 that is built according to the
present invention. The CM communication system 400 includes a CM
410 that is operable to perform upstream communication 499 to a
CMTS 430. From certain perspectives, the FIG. 4 may be viewed as
one particular embodiment of the functionality that may be
performed within the FIG. 3; clearly, the FIG. 3 may also be viewed
as described variations of embodiment that are different than the
FIG. 4. The bandwidth of the upstream communication 499, from the
CM 410 to the CMTS 430, is partitioned into a number of channels in
the FIG. 4. Again and similar to the FIG. 3, this partitioning
within the FIG. 4 may involve logical partitioning of the channels
of a single frequency band, or alternatively the partitioning may
involve physical portioning of the available bandwidth into
distinct channels that are separated in frequency.
[0069] The CMTS 430 is operable to direct upstream channel changing
for upstream data bursts from the CM 410 to the CMTS 430. As shown
in the upstream communication 499, the number of channels (shown as
a CH1, CH2, CH3, . . . , and CHn) are the available channels over
which the CMTS 430 may change the upstream data bursting of the CM
410 to the CMTS 430. The channel changing may be performed between
upstream data bursts while maintaining a high degree of robustness
and continued operation. In addition, the channel changing may be
performed between upstream data bursts without requiring
initialization and ranging processes to be performed before
changing to another channel. The present invention offers a
solution that allows the channel changing to a new channel without
requiring any prior knowledge of the state of corruption or the
capabilities of the network channel thereby offering continued
operation.
[0070] The operations performed within the CMTS 430 may be
described as follows: the CMTS 430 is operable to perform initial
channel changing processing 440 that is followed by post channel
changing processing 450. In certain embodiments, the CMTS 430 is
operable to perform the initial channel changing processing 440,
followed by channel burst profile processing 460, and ultimately
followed by performing the post channel changing processing
450.
[0071] The initial channel changing processing 440 involves using
information of a predetermined number of initial upstream data
burst profiles(s) 441. The initial upstream data burst profiles(s)
441 may include multiple upstream data burst profiles, shown as a
profile 1 442, . . . , and a profile x 449. The initial upstream
data burst profiles(s) 441 may be arranged and selectively included
so that some profiles better accommodate shorter data burst, some
profiles better accommodate longer data burst, and/or other
considerations as well. The initial upstream data burst profiles(s)
441 may be used to offer a high degree of robustness thereby
ensuring that an upstream data burst will virtually always be able
to be made from the CM 410 to the CMTS 430. For example, the
initial upstream data burst profiles(s) 441 will include at least
one profile that will enable continued transmission of an upstream
data burst from the CM 410 to the CMTS 430 between upstream data
bursts. The initial channel changing processing 440 may be viewed
as performing the necessary processing to begin and/or continue
upstream data burst transmitting functionality without requiring
the performance of the initialization and the ranging processes to
be performed when changing channels from one to another for
upstream data bursting from the CM 410 to the CMTS 430.
[0072] Subsequently, after some predetermined period of time and/or
after meeting some predetermined conditions, the CMTS 430 performs
the post channel changing processing 450. This will involve
performing the initialization and ranging processed on the new
channel to which the upstream data bursting has been changed (shown
as new channel initialization 451 and new channel ranging 452,
respectively). After these processes have been performed, then the
CMTS 430 selects a more optimal channel profile in a functional
block 453. Then, the CMTS 430 directs the CM 410 to perform using
the more optimal profile on the new channel. There may instances
where the selection of the more optimal channel profile within the
functional block 453 involves determining that the lowest order,
most robust channel profile, that has already been initially used
as shown within the initial channel changing processing 440 is in
fact the higher order channel profile that may be employed on the
new channel. In such a case, the selection of the more optimal
channel profile in the functional block 453 serves as a
verification/validation that this channel profile is in fact the
highest order channel profile available. Alternatively, the
selection of the more optimal channel profile in the functional
block 453 may involve selecting a higher order channel profile that
enables greater throughput on the new channel. In some embodiments,
the selection of the more optimal channel profile in the functional
block 453 may simply involve waiting a predetermined period of time
before switching to a higher order channel profile.
[0073] In some alternative embodiments, the channel burst profile
transition processing 460 in between performing the initial channel
changing processing 440 and the post channel changing processing
450. This channel burst profile transition processing 460 may
involve monitoring the new channel as shown in a functional block
461. In addition, the channel burst profile transition processing
460 may involve waiting until the new channel is not busy as shown
in a functional block 462. This waiting until the new channel is
not busy in the functional block 462 may involve waiting until
there is a time space between upstream data bursts, and/or waiting
until the new channel is simply completely idle for a predetermined
period of time. The channel burst profile transition processing 460
may also involve some other consideration 469 that may be used to
trigger the beginning of the post channel changing processing 450.
The channel burst profile transition processing 460 may be viewed
as an optional intermediary processing that is performed after
performing the initial channel changing from one channel to a new
channel for upstream data bursting from the CM 410 to the CMTS
430.
[0074] FIG. 5 is a system diagram illustrating an embodiment of a
CMTS system 500 that is built according to the present invention.
The CMTS 500 includes a CMTS medium access controller (MAC) 530
that operates with a number of other devices to perform
communication from one or more CMs to a WAN 580. The CMTS MAC 530
may be viewed as providing the hardware support for MAC-layer
per-packet functions including fragmentation, concatenation, and
payload header suppression that all are able to offload the
processing required by a system central processing unit (CPU) 572.
This will provide for higher overall system performance. In
addition, the CMTS MAC 530 is able to provide support for carrier
class redundancy via timestamp synchronization across a number of
receivers, shown as a receiver 511, a receiver 511, and a receiver
513 that are each operable to receive upstream analog inputs. In
addition, the CMTS MAC 530 may be operated remotely with a
routing/classification engine 579 that is located externally to the
CMTS MAC 530 for distributed CMTS applications including mini fiber
node applications. Moreover, Standard Programming Interface (SPI)
master port may be employed to control the interface to the
receivers 511, 512, and 513 as well as to a downstream modulator
520.
[0075] The CMTS MAC 530 may be viewed as being a highly integrated
CMTS MAC integrated circuit (IC) for use within the various DOCSIS
and advanced TDMA physical layer (PHY-layer) CMTS products. The
CMTS MAC 530 employs sophisticated hardware engines for upstream
and downstream paths. The upstream processor design is segmented
and uses two banks of Synchronous Dynamic Random Access Memory
(SDRAM) to minimize latency on internal buses. The two banks of
SDRAM used by the upstream processor are shown as upstream SDRAM
575 (operable to support keys and reassembly) and SDRAM 576
(operable to support Packaging, Handling, and Storage (PHS) and
output queues). The upstream processor performs Data Encryption
Standard (DES) decryption, fragment reassembly, de-concatenation,
payload packet expansion, packet acceleration, upstream Management
Information Base (MIB) statistic gathering, and priority queuing
for the resultant packets. Each output queue can be independently
configured to output packets to either a Personal Computer
Interface (PCI) or a Gigabit Media Independent Interface (GMII).
DOCSIS MAC management messages and bandwidth requests are extracted
and queued separately from data packets so that they are readily
available to the system controller.
[0076] The downstream processor accepts packets from priority
queues and performs payload header suppression, DOCSIS header
creation, DES encryption, Cyclic Redundancy Check (CRC) and Header
Check Sequence (of the DOCSIS specification), Moving Pictures
Experts Group (MPEG) encapsulation and multiplexing, and timestamp
generation on the in-band data. The CMTS MAC 530 includes an
out-of-band generator and TDMA PHY-layer interface so that it may
communicate with a CM device's out-of-band receiver for control of
power management functions. The downstream processor will also use
SDRAM 577 (operable to support PHS and output queues). The CMTS MAC
530 may be configured and managed externally via a PCI interface
and a PCI bus 571.
[0077] The CMTS MAC 530 is operable to perform initial channel
changing processing 540 that is followed by post channel changing
processing 550. In certain embodiments, the CMTS MAC 530 is
operable to perform the initial channel changing processing 540,
followed by channel burst profile processing 560, and ultimately
followed by performing the post channel changing processing 550.
The FIG. 5 shows yet another embodiment in which upstream data
burst channel changing may be performed according to the present
invention. Any of the functionality and operations described in the
other embodiments may be performed within the contact of the CMTS
system 500 without departing from the scope and spirit of the
invention.
[0078] The FIGS. 6 and 7 described below show particular
embodiments of functionality that may be performed within CMTSs
arranged according to the present invention. Related CM upstream
channel changes methods are described generically below in the
FIGS. 10 and 11. The FIG. 6 and 7 may be viewed including
functionality within CMTSs that are operable to perform the
operations described within the FIGS. 10 and 11, yet the FIGS. 10
and 11 may also be viewed as operations being performed at higher
levels besides solely a CMTS-level without departing from the scope
and spirit of the invention.
[0079] FIG. 6 is a functional block diagram illustrating an
embodiment of CMTS functionality 600 that is performed according to
the present invention. In a functional block 610, a channel is
identified that is to be changed. Then, in a functional block 620,
upstream data transmissions continue while performing the channel
changing. Initially, as shown in a functional block 630, the new
channel is operated with a first modulation density. Then, as shown
in a functional block 640, the new channel undergoes initialization
and ranging. Subsequently, the new channel is then operated at a
second modulation density as shown in a functional block 650. The
FIG. 6 shows how a new channel, to which upstream data bursting has
been changing, may first be operated using a first modulation
density and subsequently at a second modulation density after
having undergone initialization and ranging processes. The
functionality described with respect to the FIG. 6 may be viewed as
functionality and operations performed within any of the CMTSs
described within the patent application. Each of the functional
blocks within the FIG. 6 may be viewed as being associated with a
portion/portions of components within a CMTS, including processors,
CMTS MACs, and other functional blocks within a CMTS.
[0080] FIG. 7 is a functional block diagram illustrating another
embodiment of CMTS functionality that is performed according to the
present invention. In a functional block 710, a channel is
identified that is to be changed. Then, in a functional block 720,
upstream transmissions continue while performing the channel
changing. Initially, as shown in a functional block 730, the new
channel is operated a relatively lower order modulation density.
Then, as shown in a functional block 740, the new channel undergoes
initialization and ranging thereby determining a relatively higher
order modulation density that is the highest modulation density
that is possible on the new channel. Subsequently, the new channel
is then operated at this determined, higher order modulation
density as shown in a functional block 750. The FIG. 7 shows how a
new channel, to which upstream data bursting has been changing, may
first be operated using a relatively lower order modulation density
and subsequently at a higher order modulation density after having
undergone initialization and ranging processes that are used to
determine the higher order modulation density. The functionality
described with respect to the FIG. 7 may be viewed as functionality
and operations performed within any of the CMTSs described within
the patent application. Each of the functional blocks within the
FIG. 7 may be viewed as being associated with a portion/portions of
components within a CMTS, including processors, CMTS MACs, and
other functional blocks within a CMTS.
[0081] FIG. 8 is a diagram illustrating an embodiment of an
upstream communication logical channel partition 800 according to
the present invention. The various logical channels within the FIG.
8, shown as a CH1, CH2, CH3, . . . , and CHn, may be viewed as
being logical channel partitions within a single frequency
band.
[0082] Upstream data transmissions begin using a profile1 on a CH1.
Then, between upstream bursts, a channel change is directed to move
the upstream bursting to a CH2. The upstream data transmission
simply continues after having changed from the CHI to the CH2;
however, the continuation of the upstream bursts on CH2 uses a
profile2. Subsequently, there is a time gap within the upstream
data bursts, during which time the CM may range on CH2 and is able
to advance to more efficient burst profiles. The upstream bursts
then continue in the CH2 using a profile3. This profile3 may have
been identified/determined during the time gap within the upstream
bursts, perhaps using ranging bursts from the CM or perhaps using
analysis of the received data burst transmissions, or prior uses on
CH2 by that CM, or a combination of these. The profile3 may be
viewed as being an optimal upstream data burst profile for the
CH2.
[0083] After some time of the continuation of the upstream data
bursts on the CH2, another channel change is directed to move the
upstream bursting from the CH2 to a CHn. Again, the upstream data
bursts simply continue after having changed from the CH2 to the
CHn; however, the continuation of the upstream data bursts on the
CHn again uses the profile2. The profile2 may be viewed as the
upstream data burst profile that is initially used when performing
channel changing from one channel to another. As can be seen,
whenever a channel change is initiated, then the next use of a
profile is the profile2 in the embodiment shown within the FIG. 8.
It is noted, however, that there may also be multiple initial data
burst profiles, and perhaps even one per channel, or more than one
available per channel (using the multiple logical channels on a
same or nearly same center frequency).
[0084] FIG. 9A is a diagram illustrating an embodiment of example
upstream burst profiles 900 according to the present invention. A
spectrum of upstream data burst profiles may be used. Generically
speaking, a higher order profile 910 and a lower order profile may
be used. The higher order profile 910 may be viewed as having a
relatively shorter preamble, a relatively higher modulator density,
relatively weak Forward Error Correction (FEC), an equalizer tap
coefficient set1, a reflection coefficients set1, and other
parameters as required or desired. The higher order profile 910 may
be viewed as being operable on a channel whose characteristics can
support this higher order level of processing. A relatively
accurate channel estimation and channel equalization may need to be
performed to accommodate upstream data bursting using the higher
order profile 910.
[0085] The lower order profile 920 may be viewed as having a
relatively longer preamble, a relatively lower modulator density,
relatively powerful FEC, an equalizer tap coefficient set2, a
reflection coefficients set2, and other parameters as required or
desired. The lower order profile 920 may be viewed as being
operable on a channel whose characteristics are unable to support
the higher order level of processing within the higher order
profile 910. A relatively accurate channel estimation and channel
equalization may not be available or may be unable to be performed
to accommodate upstream data bursting using the higher order
profile 910, the present invention then provides operation using
the lower order profile 920.
[0086] The FIG. 9A shows a spectrum of available upstream data
burst profiles that may be used according to the present invention
to perform and continue upstream data bursting using an appropriate
degree of processing without losing data. Upstream data bursts may
be continued while switching from the higher order profile 910 to
the lower order profile 920. The upstream data bursting may
continue using the lower order profile 920, though perhaps at a
lower throughput, yet the lower order profile 920 will provide
sufficient protection to ensure that the upstream data burst will
get through even when the channel may be corrupted. The upstream
data burst profiles include a modulation density. The modulation
density may be viewed as being one parameter within an upstream
data burst profile. If desired, and as will be shown and described
in various embodiments, various profiles may be employed when
performing enhanced DOCSIS channel changing according to the
present invention; or alternatively, only various modulation
densities may be employed when performing enhanced DOCSIS channel
changing according to the present invention. Clearly, other
operational parameters may be used to differentiate and continue
upstream data bursting when performing channel changing.
[0087] FIG. 9B is a diagram illustrating an embodiment of example
modulation densities 905 according to the present invention. The
FIG. 9B shows a spectrum of modulation densities that may be
performed according to the present invention. The spectrum of
modulation densities involves higher order modulation densities and
lower order modulation densities. For example, the spectrum of
modulation densities ranges from 1024 QAM, 256 QAM, 64 QAM, 16 QAM,
and QPSK. Other modulation schemes could similarly be employed and
arranged in an increasing/decreasing order of density without
departing from the scope and spirit of the invention. The higher
order modulation densities may be viewed as including the 1024 QAM
and 256 QAM, and the lower order modulation densities may be viewed
as including the 16 QAM and QPSK. In some embodiments, a higher
order modulation density may be viewed as including only 16 QAM,
and a lower order modulation density may be viewed as including
only QPSK.
[0088] The higher order modulation densities may be used within
those channels that have been adequately initialized and ranged to
support that level of modulation density, and the low order
modulation densities may be used within those channels that have
not yet been adequately initialized and ranged to support higher
levels of modulation density. In certain embodiments, the present
invention switches directly to a lower level of modulation density
after undergoing a channel change, and then after performing
initialization and ranging, and after determining/identifying a
possible higher level of modulation density, that new channel is
operated using the higher level of modulation density.
[0089] FIG. 10 is a flowchart illustrating an embodiment of a CM
upstream channel change method 1000 that is performed according to
the present invention. In a block 1010, a channel is identified
that is to be changed. Then, in a block 1020, upstream transmission
is continued while performing the channel changing. Initially, as
shown in a block 1030, the new channel is operated a first
modulation density. Then, as shown in a block 1040, the new channel
undergoes initialization and ranging. Subsequently, the new channel
is then operated at a second modulation density as shown in a block
1050.
[0090] The FIG. 10 shows how a new channel, to which upstream data
bursting has been changed, may first be operated using a first
modulation density and subsequently at a second modulation density
after having undergone initialization and ranging processes. The
operations described with respect to the FIG. 10 may be performed
in any of the various embodiments described within the patent
application. The FIG. 10 may be viewed as being a method that is
performed at a system level, at a CMTS level, at a CM level, or
another level within any CM communication system that is built
according to the present invention. The functionality of the CMTS
functionality 600 functional block diagram may be viewed as being
the functionality specific to a CMTS. The CM upstream channel
change method 1000 may be viewed more generically as supporting the
methodology of enhanced DOCSIS upstream channel changing according
to the present invention using other devices in cooperation with a
CMTS.
[0091] FIG. 11 is a flowchart illustrating another embodiment of a
CM upstream channel change method that is performed according to
the present invention. In a block 1110, a channel is identified
that is to be changed. Then, in a block 1120, upstream transmission
is continued while performing the channel changing. Initially, as
shown in a block 1130, the new channel is operated a relatively
lower order modulation density. Then, as shown in a block 1140, the
new channel undergoes initialization and ranging thereby
determining a relatively higher order modulation density that is
the highest modulation density that is possible on the new channel.
Subsequently, the new channel is then operated at this determined,
higher order modulation density as shown in a block 1150.
[0092] The FIG. 11 shows how a new channel, to which upstream data
bursting has been changed, may first be operated using a lower
order modulation density and subsequently at a higher order
modulation density after having undergone initialization and
ranging processes. The operations described with respect to the
FIG. 11 may be performed in any of the various embodiments
described within the patent application. The FIG. 11 may be viewed
as being a method that is performed at a system level, at a CMTS
level, at a CM level, or another level within any CM communication
system that is built according to the present invention. The
functionality of the CMTS functionality 700 functional block
diagram may be viewed as being the functionality specific to a
CMTS. The CM upstream channel change method 1100 may be viewed more
generically as supporting the methodology of enhanced DOCSIS
upstream channel changing according to the present invention using
other devices in cooperation with a CMTS.
[0093] FIG. 12 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1200 that is performed according
to the present invention. In a block 1210, a channel is identified
that is to be changed. Then, in a block 1220, upstream transmission
is continued while performing the channel changing. Initially, as
shown in a block 1230, the new channel is operated using a QPSK
modulation density. Then, as shown in a block 1240, the new channel
undergoes initialization and ranging thereby determining when a 16
QAM modulation density is possible on the new channel. After it is
determined that the new channel can support the 16 QAM modulation
density, then the new channel is operated at the 16 QAM modulation
density as shown in a block 1250.
[0094] The FIG. 12 may be viewed as being an embodiment where there
are two available modulation densities (QPSK and 16 QAM) that may
be used when operating a channel, and a new channel initially
operates at a QPSK modulation density when changing to the new
channel. Only after it has been determined that the new channel can
actually support a 16 QAM modulation density does the channel begin
to operate using the 16 QAM modulation density.
[0095] FIG. 13 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1300 that is performed according
to the present invention. In a block 1310, data is initially
transmitted from a CM upstream to CMTS using a CHI and a profile1.
Then, in a block 1320, upstream data transmission is continued
while performing the channel changing from CH1 to CH2. Initially,
as shown in a block 1330, the upstream transmission on the CH2 is
performed using a profile2. Then, as shown in a block 1340, it is
determined that a maximum operable profile may be supported on the
CH2. After it is determined that the maximum operable profile may
be supported on the CH2, then the CH2 switches operation to the
maximum operable profile as shown in a block 1350.
[0096] The FIG. 13 may be viewed as being an embodiment where there
are at least two upstream data burst profiles that may be used when
operating a CH2 (to which upstream data bursting has been changed
from a CH1), and a CH2 initially operates at profile1 when changing
to the CH2. Only after it has been determined that the CH2 can
actually support a maximum operable profile does the channels begin
to operate using the maximum operable profile.
[0097] FIG. 14 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1400 that is performed according
to the present invention. In a block 1405, data is initially
transmitted upstream from a CM to a CMTS using CHI. Then, from the
CMTS, an instruction is provided to the CM to change the CM's
upstream transmission from CH1 to CH2 in a block 1410. The upstream
transmission is continued while changing channels from CH1 to CH2
as shown in a block 1420. Initially, the CH2 is operated at a
relatively lower order upstream data burst profile as shown in a
block 1430.
[0098] As shown in a block 1440, the CH2 is continuously monitored
until a time gap is detected in the upstream transmission. Then,
upon detection of the time gap, then the initialization and ranging
processes are begun as shown in a block 1441. In a block 1450, the
initialization and ranging processes are actually performed for the
CH2. The initialization and ranging processes 1450 may involve a
number of operations. As shown in a block 1451, a process 1 may be
performed. Alternatively, as shown in a block 1455, a process 2 may
be performed. Within the process 1 shown in the block 1451, channel
estimation of CH2 is performed as shown in a block 1452; after an
accurate channel estimation for the CH2 has been performed, then
direct calculation of equalizer taps for CH2 is performed in a
block 1453 using the previously generated channel estimation (from
the block 1452). In the alternative process 2 shown in the block
1455, channel estimation of CH2 need not be performed, but rather
equalizer taps calculation is performed directly for CH2 in a block
1456.
[0099] In addition, other operations may be performed in doing the
initialization and ranging processes for CH2 within the block 1450.
One possible option involves identifying a maximum operable
modulation density is identified for CH2 as shown in a block 1459.
This maximum operable modulation density is identified based on
channel estimation and/or channel equalization tap calculation that
is performed using the process 1 1451 and/or the process 2
1455.
[0100] Afterwards, in a block 1460, an appropriate upstream data
burst profile is selected. As shown in a block 1465, this selection
may be performed using the identified, maximum operable modulation
density for the CH2 (that may be identified within the block 1459).
The CH2 is then operated using the selected upstream data burst
profile as shown in a block 1470.
[0101] FIG. 15 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1500 that is performed according
to the present invention. In a block 1505, data is initially
transmitted upstream from a CM to a CMTS using CH1. Then, from the
CMTS, an instruction is provided to the CM to change the CM's
upstream transmission from CH1 to CH2 in a block 1510. The upstream
data transmissions are continued while changing channels from CH1
to CH2 as shown in a block 1520. Initially, the CH2 is operated
using a QPSK modulation density as shown in a block 1530.
[0102] As shown in a block 1540, the CH2 is continuously monitored
until a time gap is detected in the upstream transmission. Then,
upon detection of the time gap, the initialization and ranging
processes are begun as shown in a block 1541. In a block 1550, the
initialization and ranging processes are actually performed for the
CH2. The initialization and ranging processes 1550 may involve a
number of operations. As shown in a block 1551, a process 1 may be
performed. Alternatively, as shown in a block 1555, a process 2 may
be performed. Within the process 1 shown in the block 1551, channel
estimation of CH2 is performed as shown in a block 1552; after an
accurate channel estimation for the CH2 has been performed, then
direct calculation of equalizer taps for CH2 is performed in a
block 1553 using the previously generated channel estimation (from
the block 1552). In the alternative process 2 shown in the block
1555, channel estimation of CH2 need not be performed, but rather
equalizer taps calculations are performed directly for CH2 in a
block 1556.
[0103] In addition, other operations may be performed in doing the
initialization and ranging processes for CH2 within the block 1550.
In a block 1559, it is determined whether the CH2 will support a 16
QAM modulation density. This will be determined after having
performed channel estimation and/or channel equalization tap
calculations that are performed using the process 1 1551 and/or the
process 2 1555.
[0104] Afterwards, in a decision block 1560, it is queried whether
the CH2 will actually support the 16 QAM modulation density. If it
is determined that the CH2 may in fact support the 16 QAM
modulation density, then the CH2 is operated using the 16 QAM
modulation density as shown in a block 1570. Alternatively, if it
is determined that the CH2 will not support the 16 QAM modulation
density, then the CH2 is operated using the 16 QAM modulation
density as shown in a block 1565.
[0105] FIG. 16 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1600 that is performed according
to the present invention. In a block 1610, a channel is identified
that is to be changed; the changing being made from a first channel
to a second channel. Then, in a block 1620, upstream transmission
is continued while performing the channel changing. Initially, as
shown in a block 1630, the second channel is operated a first
modulation density.
[0106] Then, as shown in a block 1640, the preamble of one or more
of the subsequent data bursts on the second channel may be used to
train an equalizer that is used for the second channel. That is to
say, the equalizer taps are calculated using the preamble of one or
more of the subsequent data bursts on the second channel. This
equalizer tap calculation may be performed directly, as described
above in various embodiments, or channel estimation may first be
performed using the preamble and then that result may be used to
perform the direct equalizer tap calculation in the block 1640.
Then, as shown in a block 1650, the second channel is operated at a
second modulation density that is determined to be operable based
on the previous equalizer tap calculation.
[0107] In alternative embodiments, as shown in a block 1642, the
data of one or more of the subsequent data bursts on the second
channel may be used to train an equalizer that is used for the
second channel. That is to say, the equalizer taps are calculated
using the data of one or more of the subsequent data bursts on the
second channel. This equalizer tap calculation may be performed
directly, as described above in various embodiments, or channel
estimation may first be performed using the data and then that
result may be used to perform the direct equalizer tap calculation
in the block 1642. Then, as shown in a block 1650, the second
channel is operated at a second modulation density that is
determined to be operable based on the previous equalizer tap
calculation.
[0108] In even alternative embodiments, as shown in a block 1644,
the preamble and data of one or more of the subsequent data bursts
on the second channel may be used to train an equalizer that is
used for the second channel. That is to say, the equalizer taps are
calculated using the preamble and data of one or more of the
subsequent data bursts on the second channel. This equalizer tap
calculation may be performed directly, as described above in
various embodiments, or channel estimation may first be performed
using the data and then that result may be used to perform the
direct equalizer tap calculation in the block 1642. Then, as shown
in a block 1650, the second channel is operated at a second
modulation density that is determined to be operable based on the
previous equalizer tap calculation.
[0109] The FIG. 16 shows how a second channel, to which upstream
data bursting has been changed from a first channel, may first be
operated using a first modulation density and subsequently at a
second modulation density after having undergone equalizer tap
training (calculation of equalizer taps). The operations described
with respect to the FIG. 16 may be performed in any of the various
embodiments described within the patent application. The FIG. 16
may be viewed as being a method that is performed at a system
level, at a CMTS level, at a CM level, or another level within any
CM communication system that is built according to the present
invention. The CM upstream channel change method 1600 may be viewed
more generically as supporting the methodology of enhanced DOCSIS
upstream channel changing according to the present invention using
other devices in cooperation with a CMTS.
[0110] FIG. 17 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1700 that is performed according
to the present invention. In a block 1710, a channel is identified
that is to be changed; the changing being made from a first channel
to a second channel. Then, in a block 1720, upstream transmission
is continued while performing the channel changing. Initially, as
shown in a block 1730, the second channel is operated a first
modulation density.
[0111] Then, as shown in a block 1740, the preamble of one or more
of the subsequent data bursts on the second channel may be used to
train an equalizer that is used for the second channel. That is to
say, the equalizer taps are calculated using the preamble of one or
more of the subsequent data bursts on the second channel. This
equalizer tap calculation may be performed directly, as described
above in various embodiments, or channel estimation may first be
performed using the preamble and then that result may be used to
perform the direct equalizer tap calculation in the block 1740.
Then, as shown in a block 1750, the second channel is operated a
second modulation density when it is determined to be operable
based on the previous equalizer tap calculation.
[0112] Subsequently, as shown in a block 1760, the data of one or
more of the subsequent data bursts on the second channel may be
used to refine/re-train the equalizer that is used for the second
channel. That is to say, an improved calculation/improved estimate
of the equalizer taps are calculated using the data of one or more
of the subsequent data bursts on the second channel. This improved
equalizer tap calculation may be performed directly, as described
above in various embodiments, or channel estimation may first be
performed using the data and then that result may be used to
perform the direct equalizer tap calculation in the block 1760.
Then, as shown in a block 1770, the second channel is operated at a
third modulation density when it is determined to be operable based
on the previous, improved equalizer tap calculation.
[0113] The FIG. 17 shows how a second channel, to which upstream
data bursting has been changed from a first channel, may first be
operated using a first modulation density, subsequently at a second
modulation density, and subsequently at a third modulation density
after having undergone equalizer tap training (calculation of
equalizer taps) and equalizer tap re-training (re-calculation of
equalizer taps). The operations described with respect to the FIG.
17 may be performed in any of the various embodiments described
within the patent application. The FIG. 17 may be viewed as being a
method that is performed at a system level, at a CMTS level, at a
CM level, or another level within any CM communication system that
is built according to the present invention. The CM upstream
channel change method 1700 may be viewed more generically as
supporting the methodology of enhanced DOCSIS upstream channel
changing according to the present invention using other devices in
cooperation with a CMTS.
[0114] FIG. 18 is a flowchart illustrating another embodiment of a
CM upstream channel change method 1800 that is performed according
to the present invention. In a block 1810, a channel is identified
that is to be changed; the changing being made from a first channel
to a second channel. Then, in a block 1820, upstream transmission
is continued while performing the channel changing. Initially, as
shown in a block 1830, the second channel is operated a QPSK
modulation density.
[0115] Then, as shown in a block 1840, the preamble of one or more
of the subsequent data bursts on the second channel may be used to
train an equalizer that is used for the second channel. That is to
say, the equalizer taps are calculated using the preamble of one or
more of the subsequent data bursts on the second channel. This
equalizer tap calculation may be performed directly, as described
above in various embodiments, or channel estimation may first be
performed using the preamble and then that result may be used to
perform the direct equalizer tap calculation in the block 1840.
Then, as shown in a block 1850, the second channel is operated a 16
QAM modulation density when it is determined to be operable based
on the previous equalizer tap calculation.
[0116] Subsequently, as shown in a block 1860, the data of one or
more of the subsequent data bursts on the second channel may be
used to refine/re-train the equalizer that is used for the second
channel. That is to say, an improved calculation/improved estimate
of the equalizer taps are calculated using the data of one or more
of the subsequent data bursts on the second channel. This improved
equalizer tap calculation may be performed directly, as described
above in various embodiments, or channel estimation may first be
performed using the data and then that result may be used to
perform the direct equalizer tap calculation in the block 1860.
Then, as shown in a block 1870, the second channel is operated at a
64 QAM modulation density when it is determined to be operable
based on the previous, improved equalizer tap calculation.
[0117] The FIG. 18 shows how a second channel, to which upstream
data bursting has been changed from a first channel, may first be
operated using a QPSK modulation density, subsequently at a 16 QAM
modulation density, and subsequently at a 64 QAM modulation density
after having undergone equalizer tap training (calculation of
equalizer taps) and equalizer tap re-training (re-calculation of
equalizer taps). The operations described with respect to the FIG.
18 may be performed in any of the various embodiments described
within the patent application. The FIG. 18 may be viewed as being a
method that is performed at a system level, at a CMTS level, at a
CM level, or another level within any CM communication system that
is built according to the present invention. The CM upstream
channel change method 1800 may be viewed more generically as
supporting the methodology of enhanced DOCSIS upstream channel
changing according to the present invention using other devices in
cooperation with a CMTS.
[0118] While within the embodiment of the FIG. 18, the first,
second, and third modulation densities are shown as being QPSK, 16
QAM, and 64 QAM, respectively, those persons having skill in the
art will also appreciate that any number of modulation densities
may be used as well. For example, they may be in successively
increasing higher order of modulation density such as the first,
second, and third modulation densities being (QPSK, 16 QAM, 64 QAM
as shown in FIG. 18), or (QPSK, 64 QAM, and 1024 QAM), or (16 QAM,
64 QAM, and 256 QAM).
[0119] Alternatively, the modulation densities may be in neither
decreasing nor increasing order of modulation density such as the
first, second, and third modulation densities are explicitly shown
as being (QPSK, 64 QAM, and 16 QAM); this may be a situation where
the subsequent calculation of equalizer taps indicates that a lower
modulation density should be used (16 QAM in this case) rather than
the higher 64 QAM that was initially determined to be operable
using the initial calculation of the equalizer taps.
[0120] Those persons having skill in the art will appreciate the
increasing modulation density as it is determined to be operable
based in the equalizer tap calculations. In addition, the refining
and improvement of the modulation density may continually be
improved as it is determined to be possible upon further
refinement, adjustment, and correction of the equalizer taps.
Clearly, more that three modulation density transitions may also be
performed without departing from the scope and spirit of the
invention. If desired, whenever it is determined that a higher
modulation density may be supported, as determined by ever-improved
equalizer tap calculations in this embodiment, then the modulation
density may move to that higher modulation density to provide for
higher throughput within the system.
[0121] In view of the above detailed description of the invention
and associated drawings, other modifications and variations will
now become apparent to those skilled in the art. It should also be
apparent that such other modifications and variations may be
effected without departing from the spirit and scope of the
invention.
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